The present invention relates to a sputtering apparatus for use in thin film deposition, in which generation of anomalous discharge between a target and a backing plate, and a target presser can be prevented.
In recent years, a sputtering apparatus has been widely used in a thin film forming process for a semiconductor, a liquid crystal, an optical disk, an electronic device and the like. In particular, a sputtering apparatus for an optical disk or the like requires a remarkably reduced cost of equipment and a high throughput, and therefore, it must have a simple structure with ease of maintenance. Consequently, the equipment is simplified and the maintenance is facilitated with a structure in which an earth shield and a deposition preventing plate are integrated with each other and a target presser capable of fixing a target to a cathode is used.
Referring to FIG. 7, explanation will be made below on one example of a sputtering apparatus of a prior art. In FIG. 7, reference numeral 1 designates a sputtering target as a film forming material; and 2 denotes a backing plate comprised of copper or the like, for cooling the sputtering target 1. Reference numeral 3 designates a sputtering reactive chamber; and 4 denotes a cathode on which the sputtering target 1 and the backing plate 2 are placed. Reference numeral 5 designates a substrate holder disposed opposite to the cathode 4, for mounting thereon a substrate 6, on which a film is deposited by sputtering. Reference numeral 7 designates a power source for applying a voltage to the cathode 4 so as to generate plasma on the sputtering target 1; a vacuum exhaust pump 8 for vacuum exhausting the inside of the reactive chamber 3 into a pressure reduced atmosphere; a gas supply system 9 for supplying sputtering gas into the reactive chamber 3; a deposition preventing plate 10 comprised of stainless steel or the like and provided along the entire circumference between the substrate 6 and the backing plate 2, for preventing any deposition of sputtered particles onto the inner surface of the reactive chamber; and an insulating member 11 interposed between the deposition preventing plate 10 and the backing plate 2 and fixed to the deposition preventing plate 10 via screws or the like. The deposition preventing plate 10 and the insulating member 11 integrally serve as a target presser, which thus presses the backing plate 2, and as a result, fixes the sputtering target 1 to the cathode 4. Furthermore, reference numeral 13 designates a member for insulating the reactive chamber 3 from the cathode 4.
A description will be given below as to the operation of the sputtering apparatus and the sputtering target which are configured as described above. First, the vacuum exhaust pump 8 vacuum exhausts the inside of the reactive chamber 3 to a degree of vacuum of about 10xe2x88x925 Pa. Next, the gas supply system 9 introduces argon gas into the reactive chamber 3 so as to regulate a pressure to a degree of vacuum of about 0.67 Pa. The power source 7 applies a DC voltage or a high-frequency voltage of about 1000 V so as to generate plasma inside the reactive chamber 3, thereby forming a sputtered film on the substrate 6. At this time, the insulating member 11 keeps insulation between the deposition preventing plate 10 and each of the sputtering target 1 and the backing plate 2. The deposition preventing plate 10 functions as an earth shield, so that the plasma is generated on the sputtering target 1. Moreover, sputtering particles sputtered to portions other than the substrate 6 are deposited on the deposition preventing plate 10.
However, with the above-described configuration, a film 12 is unfavorably deposited also on the side surface of the insulating member 11 of the target presser which is in contact with the sputtering target 1 or the backing plate 2, as shown in FIG. 8. Therefore, a long-term film deposition reduces insulation resistance between the target presser and each of the sputtering target 1 and the backing plate 2, thereby causing a phenomenon such as anomalous discharge like arc discharging, or no discharging, and further, inducing deposition of foreign matters on the substrate or a non-uniform film thickness. Consequently, it is important to achieve stable discharging in order to enhance the operability of equipment or the yield of a product.
The present invention has been accomplished in view of the above-described problems experienced in the prior art. Therefore, an object of the present invention is to provide a sputtering apparatus for use in a thin film deposition, in which the operability of equipment or the yield of a product can be enhanced by suppressing anomalous discharge occurring between a target and a backing plate, and a target presser.
In general, in a sputtering apparatus, sputtering particles ejected from a surface of a sputtering target inside a reactive chamber spatter substantially linearly. When the sputtered particles collide against the surface of an object, some of the collided particles bounce and keep on spattering. In consideration of the above-described bouncing and spattering, it seems that the sputtering particles spatter even at deeper portions off linear routes extending from the target but in a quite reduced amount. In view of this, a recess is formed at an insulating member in such a manner that an unfavorable deposition film is not continuously formed on the insulating member of a target presser by sputtering. In this way, a film is hardly formed inside the recess, thus preventing any decrease in sputtering particles caused by the above-described bouncing and spattering, reducing the amount of deposited particles per unit area since the total area of the inner surface of the recess is increased as compared with the case where no recess is formed, and further, reducing the amount of deposited particles since the inside of the recess is relatively remote from a target. The non-continuous state of the deposited film has been confirmed from an insulating member having a recess in a preferred embodiment.
A sputtering apparatus according to the present invention which has been invented in the above-described manner is featured in that in a target presser also serving as an earth shield and a deposition preventing plate, a recess, more preferably, a recess constituted of two or more steps having different depths is formed in an insulating member which is in contact with a target or a backing plate. According to the present invention, it is possible to suppress anomalous discharge between the target and backing plate and the target presser, so as to reduce the maintenance frequency of equipment and enhance the operability. Moreover, it is possible to reduce pinholes, deposition of foreign matters or the like so as to make discharging stable, thereby achieving a uniform film thickness and enhancing the yield of a product.